Tetra-substituted aryl cyclic formazan dyes

ABSTRACT

Novel tetra-substituted aryl cyclic formazan dyes are useful in assaying for Li + .

FIELD OF THE INVENTION

The present invention relates to novel dyes and the qualitative andquantitative determination of lithium ions (Li⁺).

BACKGROUND OF THE INVENTION

Analytical methods for the qualitative and quantitative determination oflithium ion (Li⁺) are of interest in establishing the levels oftherapeutic lithium in humans when lithium-type medications areadministered as therapy to overcome manic depressive states in humanbeings. Such methods require that the lithium be determined in thepresence of sodium ion.

A U.S.S.R. Author Certificate No. SU1057500A discloses a material havingthe formula ##STR1## as a chromogenic agent for lithium determinaton.However, following the instructions of the Author Certificate we havebeen unable to make this compound. Moreover, the same Author Certificateappears to state that compounds of the formula ##STR2## are impossibleto use as microbiological color reagents. Biological fluids such asblood serum contain concentrations up to 150 milliMolar (mM) of sodium.Presently there are no reagents with which Li⁺ can be correctlydetermined in the presence of sodium.

SUMMARY OF THE INVENTION

According to the present invention there is provided a class of noveltetra-substituted aryl cyclic formazan dyes which are useful in theanalytical determination of Li⁺. Such determination can be carried outin the presence of sodium, particularly in the presence of amounts ofsodium usually found in biological fluids. The dyes are useful in thequantitative and qualitative analysis of lithium concentrations as lowas 0.03 mmolar.

In a preferred embodiment the dyes have the structure ##STR3## Xrepresents CN or NO₂ ; Y represents --CH₂ CH₂ --, --CH₂ CH₂ CH₂ -- or--CH₂ CH₂ --O--CH₂ CH₂ --; and

R₁, R₂, R₃ and R₄ each independently represent alkyl having up to 12carbon atoms, halogen (e.g. Cl⁻, B_(r) ⁻, I⁻), alkoxy having up to 12carbon atoms or NO₂.

DETAILS OF THE INVENTION

The analytical method for Li⁺ comprises the step of complexing Li⁺ witha dye of the invention. Such method can involve:

(a) preparing a curve which relates lithium concentration to changes inabsorbance, at a specified wavelength (e.g. greater than 500 nanometers,preferably in the range 550 to 650, more preferably 600 to 620)nanometers, of a series of solutions comprising the same concentrationof a tetra-substituted aryl cyclic formazan dye, a base and varyingknown concentrations of lithium;

(b) determining the absorbance, at the specified wavelength of asolution containing the (i) same dye and base concentrations as in step(a) and (ii) an aliquot of an aqueous solution containing an unknownconcentration of lithium; and

(c) reading the lithium concentration from the curve prepared in step(a) corresponding to the absorbance determined in step (b).

Ideally the method is carried out in pH ranges of 7 to 11.

The method can be used to determine Li⁺ in the presence of sodium.Accuracy of such a determination can be enhanced by adding to thesolution of (a) above an amount of sodium expected in the unknown. Inbiological fluids amounts up to 150 mM should be sufficient. It has beendetermined that absorbance of solutions containing the dye, the base,and sodium ion in concentrations up to 150 millimoles/liter (mM/L), isconstant. See Table III. Therefore, shifts caused by the presence of Li⁺can be determined in the presence of sodium. This also demonstrates thehigh selectivity of the dyes of this invention for lithium as comparedto sodium.

Useful bases which can be used in the method include organic andinorganic material such as morpholine, triethylamine, ammonium hydroxideand TRIS buffer.

Representative dyes of this invention are listed in the following TableI.

                  TABLE I                                                         ______________________________________                                        Dye No. X       Y             R.sub.1                                         ______________________________________                                        1       CN      --CH.sub.2 CH.sub.2 CH.sub.2 --                                                             OCH.sub.3                                       2       CN      --CH.sub.2 CH.sub.2 CH.sub.2 --                                                             CH.sub.3 O--C.sub.6 H.sub.4 O                   3       CN      --CH.sub.2 CH.sub.2 CH.sub.2 --                                                             C.sub.4 H.sub.9                                 4       CN      --CH.sub.2 CH.sub.2 CH.sub.2 --                                                             C.sub.6 H.sub.13 --O--C.sub.6 H.sub.4           ______________________________________                                                                      --O                                             Dye No.  R.sub.2     R.sub.3      R.sub.4                                     ______________________________________                                        1        NO.sub.2    OCH.sub.3    NO.sub.2                                    2        NO.sub.2    CH.sub.3 OC.sub.6 H.sub.4 O                                                                NO.sub.2                                    3        NO.sub.2    C.sub.4 H.sub.9                                                                            NO.sub.2                                    4        NO.sub.2    C.sub.6 H.sub.13 OC.sub.6 H.sub.4 --O                                                      NO.sub.2                                    ______________________________________                                    

The dyes of the invention are prepared according to scheme I or schemeII, infra.

The following examples illustrate the procedures used to make thecompounds of this invention.

EXAMPLE 1

Dyes 1 and 3 of Table I were made using reaction scheme I as exemplifiedin the described actual preparation. ##STR4##

PREPARATION OF DYE 3, TABLE I Step 1

A stirred solution of p-n-butylphenol (30.0 g, 0.22 mole) in 400 mL CH₂Cl₂ in a 500 mL Erlenmeyer flask was cooled to 5° C. in an ice/waterbath. To this, a solution of HNO₃ (conc, 16 mL) in 20 mL of H₂ O wasadded slowly enough to maintain a temperature of 5° C. After a further15 minutes, the reaction flask was put in the refrigerator (8° C.) for 3hours.

The product was isolated by a normal ether extraction affording a yellowoil, which thin layer chromatography (ligroin) indicated to be twocomponents. The mixture was purified with column chromatography usingligroine as eluant.

Step 2

A 1000 mL, three-necked, round bottom flask, was equipped with anoverhead stirrer, condenser, and N₂ inlet. 4-n-butyl-2-nitrophenol (15g, 0.077 mole) was added followed by 250 mL of DMF. The mixture wasstirred. NaH (2.2 g, 0.09 mole) was slowly added with good stirring. Thereaction mixture turned very orange. The mixture was heated at 70° C.for 30 minutes; then 1,3-dichloropropane (4.3 g, 0.038 mole) wascombined with a minimal amount of DMF (15 mL) and added to the reactionmixture through the top of the condenser. The mixture was heated to 130°C. and there maintained for 18 hours.

The reaction mixture was passed into a one-necked, round bottom flask.Most of the DMF was stripped on a rotoevaporator leaving an orange oil.The product was isolated by pouring the oil into 600 mL of water andextracting the oil into CH₂ Cl₂ /ether, followed by a hexane wash.

Step 3

The product of Step 2 was combined with 150 mL of dry tetrahydrofuranand 0.5 g of 10% palladium on carbon in a Parr bottle. The bottle wascharged with 46 psi of hydrogen and reduced on a Parr shaker. After 2hours, the reaction consumed 20 psi of hydrogen, and the reactionmixture changed from yellow to a colorless solution. Thin layerchromatography (CH₂ Cl₂) indicated the reaction was complete. Thereaction mixture was filtered through a sintered glass funnel filledwith a layer of Na₂ SO₄ atop a pad of celite to remove the palladium oncarbon. The pad was washed with THF, and strip filtered on therotoevaporator.

Step 4

The product of Step 3 l (2.1 g) was combined with 10 mL of CHCl₃ in a100 mL round bottom flask equipped with a stirring bar, short condenser,and N₂ inlet. NH₄ NO₃ (0.9 g, 0.01 mole), followed by thetrifluoroacetic anhydride (25 mL, 0.176 mole) was added to the solution.A white solid precipitate formed, making stirring difficult. Continuedaddition of the anhydride made stirring easier. After complete addition,the suspension was stirred for 10 minutes, followed by the addition of25 mL of CHCl₃. After 3 hours, a solution was obtained which was stirredabout 20 hours.

The solution was poured into about 800 mL of H₂ O and the product wasextracted with a CH₂ Cl₂ /ether mixture.

Step 5

The product of Step 4 (1.88 g) was combined with 10 mL of methanol in a125 mL Erlenmeyer flask equipped with a stirring bar. Stirring slowly,40 mL of 10% NaOH was added to form a solution. The solution was stirredfor 16 hours. A solid formed that was collected and air dried.

The solid was purified by dissolving it in acetone and slowly adding 1.5times the volume of water. A fine precipitate resulted with stirring andscratching. The precipitate was filtered and dried.

Step 6

A stirred solution of cyanoacetic acid (0.43 g, 0.005 mole), andnickelous nitrate (0.5 g, template) in 100 mL 10% aq. pryidine wascooled to 0° C. in an ice/CH₃ OH bath. A solution of the product of Step5 (0.46 g, 0.001 mole) in 10 mL formic acid, was chilled to 0° C. in anice/CH₃ OH bath and diazotized with nitrosyl sulfuric acid (0.31 mL,0.002 mole). The diazotized solution was added to the cyanoacetic acidsolution with a color change from pale blue to deep red. The mixture wasstirred an additional hour at 0° C. and then poured over a liter of icewater and acidified with concentrated HCl to a pH of 3. The reactionmixture was placed in the refrigerator overnight to yield a very fineprecipitate. It was filtered, washed well with H₂ O and dried. Thinlayer chromatography (CH₂ Cl₂) indicated desired product dye 3.

Dye 3 was purified by eluting it though a short column of silica with75/25 CH₂ Cl₂ /hexane until color no longer came off the column toafford 157 mg (30%) of pure compound: mp 251°-252° C., ¹ H NMR (CDCl₃) δ0.95 (t, 6H), 1.15-1.6 (m, 8H), 2.45 (t, 2H), 2.9 (t, 4H), 4.5 (t, 4H),7.6 (s, 2H), 7.82 (s, 2H), 15.7 (s, NH). Anal. Calcd for C₂₅ H₂₉ N₇ O₆ :C, 57.4; H, 5.5. Found: C, 57.6; H, 5.7. HRMS, Calcd for C₂₅ H₂₉ N₇ O₆ :523,2179. Obsvd: 523,2216.

Compound 1 was made using Scheme I with the appropriately substitutednitrophenol in Step 1. Dye 1 ¹ H NMR (CDCl₃) δ 2.4 (m, 2H), 3.75 (s,6H), 4.44 (bt, 4H), 6.9 (s, 8H), 7.42 (s, 2H), 7.60 (s, 2H), 15.36 (s,NH). Anal. Calcd for C₁₉ H₁₇ N₇ O₈ : C, 48.4; H, 3.6; N, 20.8. Found: C,47.9; H, 3.7; N, 19.2.

EXAMPLE 2

Dyes 2 and 4 were made according to reaction scheme II and theaccompanying preparation. ##STR5##

PREPARATION OF METHOXYPHENOXY-NITRO-CYANO-FORMAZAN, (DYE 2) Step 1

1,3-Bis(2-amino-4-chloro-5-nitrophenoxy)propane was prepared from2-amino-4-chloro-5-nitrophenol (18.9 g, 0.10 mole) and1,3-dichloropropane (6.2 g, 0.055 mole) in a manner similar to that usedin Step 2 of Example 1 above. The crude reaction mixture was poured intoa large volume of water yielding a solid. The solid was purified bydissolving it in acetone and slowly adding 1.5 times the volume ofwater. A fine precipitate results with stirring and scratching. Theprecipitate was filtered and dried.

Step 2

A 100 mL three-necked, round bottom flask was fitted with a condenser,stirring bar, N₂ inlet and oil bath. With good stirring, p-methoxyphenol(6.21 g, 0.05 mole) followed by 20 mL of dry pyridine was added to theflask to obtain a solution. Potassium-t-butoxide (5.7 g, 0.05 mole) wasthen added and the solution changed from tan to pale green. Stirring wascontinued for 15-20 minutes. The condenser was replaced with adistillation head, and using an aspirator, t-bityl alcohol (bp 83° C.),which was generated, was removed. Again, the distillation head wasreplaced with a condenser. The compound in Step 1 (8.8 g) was added andthe mixture was heated at 110° C. overnight (17 hours).

The resulting brown solution was poured into a one-necked, round bottomflask. Pyridine was removed using a rotoevaporator leaving a brown tackymaterial. The material was dissolved in 1:1 CH₂ Cl₂ :ether. A very darksolid precipitate was removed by filtration. The filtrate was washedwith H₂ O and a saturated NaCl solution and dried over Na₂ SO₄. Thesolvent was removed on the rotoevaporator, leaving a yellow solid.

Step 3

The diamine (1 mmol) prepared in Step 2 above was diazotized usingacetic acid/proprionic acid (5:1) as the diazotization solvent alongwith NaNO₂ (0.14 g, 0.002 mole)/conc HCl (0.6 mL). The bis-diazonium ionwas coupled with cyanoacetic acid as in the preparation of dye 3.

Dye 2 was isolated as a microcrystalline deep red solid that waspurified by chromatography (11%) mp>200° C.; FDMS, 665 (M⁺); ¹ H NMR(CD₂ Cl₂) δ 2.32 (m, 2 H), 3.70 (s, 6 H), 4.40 (t, 4H), 6.82 (bs, 8H),7.38 (s, 2H), 7.55 (s, 2H), 15.4 (s, NH).

Dye 4 was isolated by extraction (CH₂ Cl₂) and purified bychromatography (CH₂ Cl₂) to give a waxy red oil (30%): FDMS, 295 (M⁺); ¹H NMR (CDCl₃) δ 0.91 (m, 6H), 1.15-1.9 (m, 16H), 2.4 (m, 2H), 3.95 (t,4H), 4.49 (t, 4H), 6.92 (s, 8H), 7.48 (s, 2H), 7.64 (s, 2H), 15.5 (s,NH). ANAL. Calcd for C₄₁ H₄₅ N₇ O₁₀ : C, 61.9; H, 5.7; N, 12.3. Found:C, 62.3; H, 5.8; N, 11.9.

The method of this invention is also practiced with a dry analyticalelement. A variety of different elements, depending on the method ofassay, can be prepared in accordance with the present invention.Elements can be configured in a variety of forms, including elongatedtapes of any desired width, sheets, slides or chips. The simplestelement can be composed of an absorbent carrier material, for example, athin sheet of a self-supporting absorbent or bibulous material, such asfilter paper or strips, which contains the dyes of this invention.

The elements can have two or more discrete zones, either in the samelayer or superimposed. At least one of the zones is preferably a porousspreading zone. The other zones can be reagent zones or registrationzones as those zones are known in the art, additional spreading zones,radiation-blocking or filter zones, subbing zones or barrier zones. Thezones are generally in fluid contact with each other, meaning thatfluids, reagents and reaction products (for example, color dyes) canpass or be transported between superposed regions of adjacent zones. Inother words, when the element is contacted with fluid, all reagents ofthe analytical composition become mixed and can readily move within theelement as a composition. Preferably, each zone is a separately coatedlayer, although two or more zones can be separate areas in a singlelayer of the element. Besides the references noted above, suitableelement components are described also, for example in U.S. Pat. Nos.4,042,335 (issued Aug. 16, 1977 l to Clement), 4,132,528 (issued Jan. 2,1979 to Eikenberry et al), and 4,144,306 (issued Mar. 13, 1979 toFigueras).

Useful absorbent carrier materials are insoluble and maintain theirstructural integrity when exposed to water or biological fluids such aswhole blood or serum. Useful elements can be prepared from paper, porousparticulate structures, porous polymeric films, cellulose, glass fibers,woven and nonwoven fabrics (synthetic and nonsynthetic) and the like.Useful materials and procedures for making such elements are well knownin the art as exemplified in U.S. Pat. Nos. 3,092,465 (issued June 4,1963 to Adams et al), 3,802,842 (issued Apr. 9, 1974 to Lange et al),3,915,647 (issued Oct. 28, 1975 to Wright), 3,917,453 (issued Nov. 4,1975 to Milligan et al), 3,936,357 (issued Feb. 3, 1976 to Milligan etal), 4,248,829 (issued Feb. 3, 1981 to Kitajima et al), 4,255,384(issued Mar. 10, 1981 Kitajima et al), 4,270,920 (issued June 2, 1981 toKondo et al) and 4,312,834 (issued Jan. 26, 1982 to Vogel et al).

Preferably, the absorbent carrier material is a porous spreading zone.This zone can be self-supporting (that is, composed of a material rigidenough to maintain its integrity), but preferably it is carried on aseparate support. Such a support can be any suitable dimensionallystable, and preferably, nonporous and transparent (that is, radiationtransmissive) material which transmits electromagnetic radiation of awavelength between about 200 and about 900 nm. A support of choice for aparticular element should be compatible with the intended mode ofdetection (fluorescence, transmission or reflectance spectroscopy).Useful supports can be prepared from paper, metal foils, polystyrene,polyesters, polycarbonates, cellulose esters and others known in theart.

The porous spreading zone can be prepared from any suitable fibrous ornon-fibrous material or mixtures of either or both. The void volume andaverage pore size of this zone can be varied depending upon the useintended.

Useful spreading zones can be prepared using fibrous materials, eithermixed with a suitable binder material or woven into a fabric, asdescribed in U.S. Pat. No. 4,292,272 (issued Sept. 29, 1981 to Kitajimaet al), polymeric compositions or particulate materials, for example,beads bound together with or without binding adhesives, as described inU.S. Pat. Nos. 3,992,158 (issued Nov. 16, 1976 to Przybylowicz et al),4,258,001 (issued Mar. 24, 1981 to Pierce et al) and 4,430,436 (issuedFeb. 7, 1984 to Koyama et al) and Japanese Patent Publication57(1982)-101760. It is desirable that the spreading zone beisotropically porous, meaning that the porosity is the same in eachdirection in the zone as caused by interconnected spaces or poresbetween particles, fibers or polymeric strands.

The method can be manual or automated. In general, in using the dryelements, a Li⁺ determination is made by taking an element from a supplyroll, chip packet or other source and physically contacting it with asample (for example, up to 200 μl) of the liquid to be tested so thatthe sample and reagents within the element become mixed. Such contactcan be accomplished in any suitable manner, for example, by dipping orimmersing the element into the sample or, preferably, by spotting theelement by hand or machine with a drop of the sample with a suitabledispensing means.

The following examples illustrate the use of the dyes of this inventionto assay Li⁺.

EXAMPLE 3 Determination of the Concentration of an Unknown Lithium IonSolution in the Absence of Sodium Ion

A standard calibration curve which relates the absorbance (at 612 nm) ofthe formazan dye solution and concentrations of lithium ion (Li⁺) wasgenerated from the following measurements.

A 6.7×10⁻⁵ M solution of dye 2 of Table I in 10% aqueous dioxane wasmade up by dissolving the appropriate amount of dye in the aqueousdioxane in a volumetric flask. A 3.0 ml aliquot of this solution wastransferred to a 1 cm curvette and 0.05 ml of triethylamine was added. Areference solution of 3.0 ml of 10% aqueous dioxane containing 0.05 mlor triethylamine was used in the reference curvette for furtherabsorbance measurements.

In separate measurements, the absorbance (at 612 nm) of theabove-mentioned dye and base solution together with 0.05 ml of each ofsix known aqueous lithium chloride solutions were recorded. The sixlithium chloride solutions and resulting final Li⁺ concentrations thatwere used are indicated below.

a. 0.05 ml of 0.02M LiCl to give 0.323 mM Li⁺

b. 0.05 ml of 0.03M LiCl to give 0.484 mM Li⁺

c. 0.05 ml of 0.04M LiCl to give 0.645 mM Li⁺

d. 0.05 ml of 0.05M LiCl to give 0.806 mM Li⁺

e. 0.05 ml of 0.065M LiCl to give 1.048 mM Li⁺

f. 0.05 ml of 0.075M LiCl to give 1.210 mM Li⁺

The absorbances for each of the above known Li⁺ concentrations are shownin Table II, along with solutions of lower concentration used todetermine a lower detection limit for Li⁺.

                  TABLE II                                                        ______________________________________                                        Detection Limit of Li.sup.+ Using 6.7 × 10.sup.-5 M                     Dye 2, (Table I) and Triethylamine in                                         10% Aqueous Dioxane                                                           Conc Li.sup.+ (mM)                                                                           Abs (612 nm)                                                   ______________________________________                                        0.0322         0.521                                                          0.2419         0.893                                                          0.3226         0.993                                                          0.4839         1.110                                                          0.6452         1.200                                                          0.8065         1.227                                                          1.0484         1.320                                                          1.2097         1.352                                                          ______________________________________                                    

The concentration of Li⁺ in an unknown solution was determined in thefollowing way:

a. 0.05 ml of the unknown solution was added to 3.05 ml of theabove-mentioned dye and base solution and the absorbance at 612 nmrecorded.

b. from the standard calibration curve, the Li⁺ concentration thatcorresponds to this measured absorption was read.

Table II shows that concentrations as low as 0.0322 mM can be determinedusing the dyes of this invention.

All the dyes of Table I can be used according to this example for Li⁺determinations.

EXAMPLE 4

This example was designed to determine the effect of concentrations ofsodium ion (in the physiologically important range of 120-150 mM) on themeasurement of Li⁺.

This experiment was run with solutions which contained differentrelative concentrations of Li⁺ and sodium ion but the sameconcentrations of dye 2 (5.4×10⁻⁵ M) and base. The absorbances of thesesolutions were measured and the data are shown in Table III.

                  TABLE III                                                       ______________________________________                                        Solution No.                                                                           Li.sup.+  (mM)                                                                             Na.sup.+  (mM)                                                                          Abs (612 nm)                                  ______________________________________                                        1        1.08         0         1.175                                         2        1.08         120       1.183                                         3        1.08         133       1.164                                         4        1.08         150       1.158                                         5        0            120       0.720                                         6         0.308       133       0.960                                         ______________________________________                                    

These results indicate that Li⁺, in the physiological range of 0.3 to1.0 mM, can be determined in the presence of as much as 150 mM Na⁺.

EXAMPLE 5 Determination of the Concentration of Unknown Li⁺Concentrations in the Presence of Na⁺

Since the absorbance due to Li⁺ is unaffected within the experimentalerror of measurement in the presence of sodium ion in the range of 120mM-150 mM (see Table III) Li⁺ was determined in the presence of thisrange on concentrations of Na⁺ as follows.

A 6.7×10⁻⁵ M solution of dye 4 of Table I in 30% aqueous dioxane wasmade up by dissolving the appropriate number of milligrams of dye in theaqueous dioxane in a volumetric flask. A 2.4 ml aliquot of this solutionwas transferred to a 1 cm curvette and 0.05 ml of morpholine ortriethylamine was added along with 0.20 ml or 2M sodium chloride and 0.3ml of water to give a standard dye solution which contained 133 mM Na⁺.A reference solution of 3.0 ml of 10% aqueous dioxane containing 0.05 mlor morpholine or triethylamine was used in the reference curvette forfurther absorbance measurements.

In separate measurements, the absorbance (at 612 nm) of theabove-mentioned dye and base and NaCl solution together with 0.05 ml ofeach of the five known aqueous LiCl solutions were recorded as inexample 3. The data obtained was plotted to give a standard calibrationcurve in the presence of sodium ion.

From this new standard calibration curve, the concentration of anunknown lithium solution that contains Na⁺ in the concentration range of120-150 mM/L (such as that encountered in human serum) can be determinedby measuring the absorbance and reading the concentration from thecalibration curve in the same manner as that used in example 1.

EXAMPLE 6

An element was prepared comprising a poly(ethylene terephthalate)support; a reagent layer comprised of gelatin, Triton X-100 surfactant(Rohm & Haas, Philadelphia, Pa.), tris(hydroxymethyl) aminomethanebuffer pH 8.5 (Sigma Chemical Co., St. Louis, Mo.) and Dye 2, coated indiethyl lauramide or dioctyphenyl phosphonate; a subbing layer comprisedof poly(N-isopropylacrylamide); and a spreading layer comprised oftitanium dioxide, cellulose acetate, Estane™ (B. F. Goodrich, Cleveland,Ohio) and Triton X-100.

This coating was then spotted with several drops of a 1 molar solutionof lithium chloride in TRIS buffer, pH 8.5. A color change from red toblue was seen, indicating that this element is suitable for thequalitative determination Li⁺.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

We claim:
 1. A dye having the structure ##STR6## wherein X represents CNor NO₂ ;Y represents CH₂ CH₂, CH₂ CH₂ CH₂, or CH₂ CH₂ --O--CH₂ CH₂ ; andR₁, R₂, R₃ and R₄ each independently represent butyl, halogen, alkoxy orNO₂.
 2. A dye according to claim 1 wherein R₁, R₂, R₃ and R₄ eachindependently represent NO₂, methoxy, butyl, methoxyphenoxy orhexyloxyphenoxy.
 3. A dye according to claim 1 selected from Table I asfollows:

                  TABLE I                                                         ______________________________________                                        Dye No. X       Y             R.sub.1                                         ______________________________________                                        1       CN      --CH.sub.2 CH.sub.2 CH.sub.2 --                                                             OCH.sub.3                                       2       CN      --CH.sub.2 CH.sub.2 CH.sub.2 --                                                             CH.sub.3 O--C.sub.6 H.sub.4 O                   3       CN      --CH.sub.2 CH.sub.2 CH.sub.2 --                                                             C.sub.4 H.sub.9                                 4       CN      --CH.sub.2 CH.sub.2 CH.sub.2 --                                                             C.sub.6 H.sub.13 --O--C.sub.6 H.sub.4           ______________________________________                                                                      --O                                             Dye No.  R.sub.2     R.sub.3      R.sub.4                                     ______________________________________                                        1        NO.sub.2    OCH.sub.3    NO.sub.2                                    2        NO.sub.2    CH.sub.3 OC.sub.6 H.sub.4 O                                                                NO.sub.2                                    3        NO.sub.2    C.sub.4 H.sub.9                                                                            NO.sub.2                                    4        NO.sub.2    C.sub.6 H.sub.13 OC.sub.6 H.sub.4 --O                                                      NO.sub.2                                    ______________________________________                                    